sbw1
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- Oct 10, 2006
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Your GPS doesn't care about where the magnetic North Pole is. It uses a datum structure known as WGS84 which is the standard used by our GPS constellation and receivers.
Your compass on the other hand does care.
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My understanding of the issue is chart plotters are becoming increasingly inaccurate as as result of this naturally occurring event. Are you saying it's business as usual?
Thanks for the explanation. I run with true North and chart up on my plotter all the time, but like most have the option of using magnetic and follow course in the plotter set up. While I do not plan on doing that does a pole shift degrade plotter accuracy if it is set to magnetic North and follow course?It's business as usual. The next gen of GPS satellites launched from Vandenberg a few months back. More accurate and hardened against people who do bad things. It still uses WGS84 which is a mathematical model of the Earth and is completely independent of magnetic north. I don't know of any devices which use both a magnetic heading and GPS at the same time. On large cargo ships, they put one GPS antenna on the bow and one on the stern so that their electronics show which bearing the bow is pointing to ....even at anchor.
The magnetic pole allegedly will "flip" to the South Pole at some point in the next 1,000-10,000 years or so. I doubt I will have my Sea Ray when that happens.
The pole shift would affect the fluxgate compass. Do we need to just re-orientate the fluxgate or maybe there's a place to enter the magnetic declination or something?I had to look up the manual on your E125 to answer this. Basically all of your charts are built on True North which uses the WGS84 datum standard. I didn't see an option on the E125 to set it to magnetic north (it might be there someplace in the 400+ pages). That would automatically throw your position off depending where you are in the world because your position on the chart plotter would not match the map.
In that scenario, your charts would be running off the GPS (true north) and your position on the chart would be magnetic north. If that is even possible on the E125, I can't imagine a scenario where that would be a good idea because you won't be where you think you are.
If you are saying that you are using your magnetic compass AND watch your E125 which is in True North mode....okay......I probably do that sometimes as well when I cross large bodies of water.
Yea it's in there - you need to set either True or Mag in the system. If you set Mag then you need to input the offset (declination) depending what latitude/longitude you boat. The GPS data is then offset to the Mag position which if done correctly the displayed position and track will then match the compass. I keep the electronics set to True with the knowledge of the declination on the compass in my area. The charts show both so I can navigate with either. Declination for where I live is almost -7 degrees and the Bahamas becomes right at -9 degrees; or, I should say "was".....I had to look up the manual on your E125 to answer this. Basically all of your charts are built on True North which uses the WGS84 datum standard. I didn't see an option on the E125 to set it to magnetic north (it might be there someplace in the 400+ pages). That would automatically throw your position off depending where you are in the world because your position on the chart plotter would not match the map.
In that scenario, your charts would be running off the GPS (true north) and your position on the chart would be magnetic north. If that is even possible on the E125, I can't imagine a scenario where that would be a good idea because you won't be where you think you are.
If you are saying that you are using your magnetic compass AND watch your E125 which is in True North mode....okay......I probably do that sometimes as well when I cross large bodies of water.
I'm pretty sure magnetic North is an option, although I don't know the reason. As mentioned earlier I run true North. However, I routinely keep a written paper log of my magnetic heading for each leg of a trip in case the electronic stuff goes down. We are frequently off shore and out of sight of land, and even when within 10 miles of land the visibility is frequently less than a mile. The manual compass and a watch keeps you properly oriented if the technology fails, which has happened on ocassion.I had to look up the manual on your E125 to answer this. Basically all of your charts are built on True North which uses the WGS84 datum standard. I didn't see an option on the E125 to set it to magnetic north (it might be there someplace in the 400+ pages). That would automatically throw your position off depending where you are in the world because your position on the chart plotter would not match the map.
In that scenario, your charts would be running off the GPS (true north) and your position on the chart would be magnetic north. If that is even possible on the E125, I can't imagine a scenario where that would be a good idea because you won't be where you think you are.
If you are saying that you are using your magnetic compass AND watch your E125 which is in True North mode....okay......I probably do that sometimes as well when I cross large bodies of water.
Wow, never thought of that. Does that mean you have to jump out of the way when you flush to avoid being "painted"?All I want to know is, will Garmin send me an update - and will our toilets flush backward when the poles flip?
Interesting question. Would be good to have response from someone who understands the issue.The pole shift would affect the fluxgate compass. Do we need to just re-orientate the fluxgate or maybe there's a place to enter the magnetic declination or something?
The pole shift would affect the fluxgate compass. Do we need to just re-orientate the fluxgate or maybe there's a place to enter the magnetic declination or something?
So, in a nutshell, not an issue when operating in true North mode, and of no practical significance if navigating a magnetic heading using modern fluxgate equipment and plotters. Thanks. Great answer.For what it is worth:
12-21-17, 06:26 AM (This post was last modified: 04-04-18 02:40 PM by Chuck - Raymarine - Moderator.)
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Derek - Raymarine - Moderator
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Deviation, Variation and Heading Offset
All compasses, whether Electronic or Fluid filled - 'Wet-card' type will be subject to both Deviation and variation which will affect the accuracy and the performance of the compass.
Deviation is caused by local magnetic distortion of the earth’s magnetic field by ferrous materials, electric/ electronic devices, mobile phones, loudspeakers etc . . mounted nearby. The Effect of deviation can be reduced by correct location of the compass sensor, click here and and click here for more information regarding compass location and calibration.
The deviation figure displayed by the Autopilot is the measured value of the maximum error plus the minimum error, between the expected compass heading and the measured compass heading, when the compass sensor is calibrated (Linearised). Correction to compensate for this distortion is applied automatically to each heading after the linearisation process is completed, to provide an accurate magnetic heading display.
The electronic compasses, whether the earlier style Fluxgate sensor or the current EV1 or EV2 sensor have the capability to compensate (Automatically Linearise) for local Deviation, whereas typical fluid filled or 'wet card' compasses have to be manually adjusted with magnets by a qualified compass adjuster. You can click here for more information
Variation is the actual local difference between Magnetic North and True North, this is a global magnetic anomaly, the value of variation changes depending on geographical location and date, since the location of Magnetic North changes with time. Variation cannot be compensated for mechanically or electronically, but is a value which is used by navigators to correct locally for True heading based navigation or plotting magnetic based courses onto paper charts which are generally orientated to True North.
Heading offset is a value which is applied to the displayed heading of an electronic compass in order to accurately align it with the correct magnetic bearing.
Typically, once an older electronic fluxgate compass has been linearised, there might be a small but constant positive or negative error on every heading once the deviation has been identified and applied.
The heading offset enables the user to effectively ‘rotate’ the compass through a uniform angle clockwise or anticlockwise to eliminate this constant error and enable corrected bearings to be displayed.
Later electronic compass sensors have built-in heading offset correction and so this manual adjustment is rarely needed.
RAYFAQ#
Still need to call Al !!Your GPS doesn't care about where the magnetic North Pole is. It uses a datum structure known as WGS84 which is the standard used by our GPS constellation and receivers.
Your compass on the other hand does care.